1. Field of the Invention
The present invention relates generally to a device for judging the type of color of a document which can be utilized for, for example, a digital color copying machine and a printer capable for multicolor printing, and more particularly, to a device for judging the type of color of a document for judging whether a document is a color document containing chromatic color information or a black-and-white document containing only achromatic color information.
2. Description of the Prior Art
Some digital color copying machines being commercially available have a mechanism for judging the type of color of a document for prescanning the document to read its image data and automatically judging from the image data read whether the document is a black-and-white document containing only achromatic color information or a color document containing chromatic color information.
In the mechanism for judging the type of color of a document in such a digital color copying machine being commercially available, the image data read is stored once in an image memory, the composition ratio of yellow (hereinafter referred to as "Y"), magenta (hereinafter referred to as "M") and cyan (hereinafter referred to as "C") colors constituting the data stored is investigated for each pixel, and the type of color of the document is judged on the basis of the results of the investigation.
When it is judged that the document is a black-and-white document containing only achromatic color information. copies are made using black (hereinafter referred to as "Bk") toner particles. On the other hand, when it is judged that the document is a color document containing chromatic color information, color copies are made using toner particles in three colors, that is, Y, M and C colors or toner particles in four colors, that is, Y, M, C and Bk colors.
The above described mechanism for judging the type of color of a document has the disadvantages in that a highcost image memory is an indispensable constituent element because the image data read must be stored once in the image memory so as to judge the type of color of the document, and the type of color of the document cannot be judged in real time on the basis of the image data read because the image data is stored once in the image memory.